U.S. patent number 6,804,296 [Application Number 09/991,988] was granted by the patent office on 2004-10-12 for method for protection of data reproduction according to medium protection data, position information, first and second apparatus protection data and a film classification system to determine whether main data at specified positions are reproduced in their entirety, partially, or not at all, and data.
This patent grant is currently assigned to Victor Company of Japan, Ltd.. Invention is credited to Takayuki Sugahara.
United States Patent |
6,804,296 |
Sugahara |
October 12, 2004 |
METHOD FOR PROTECTION OF DATA REPRODUCTION ACCORDING TO MEDIUM
PROTECTION DATA, POSITION INFORMATION, FIRST AND SECOND APPARATUS
PROTECTION DATA AND A FILM CLASSIFICATION SYSTEM TO DETERMINE
WHETHER MAIN DATA AT SPECIFIED POSITIONS ARE REPRODUCED IN THEIR
ENTIRETY, PARTIALLY, OR NOT AT ALL, AND DATA MEDIUM THEREFOR
Abstract
In a reproduction apparatus, for reproducing an original signal
conveyed as main data by a data medium such as a recording disk or
broadcasting system, with medium protection data which are specific
to the data medium being conveyed together with the main data, the
apparatus includes a section for generating apparatus protection
data which are specific to the reproduction apparatus, a section
for combining the apparatus protection data with the medium
protection data to define a protection level, and a section for
applying the protection level to restrict reproduction of the
original signal, with stepwise variations in restriction occurring
in accordance with changes in protection level. The medium
protection data may include information for specifying restricted
reproduction of portions of the original signal, such as by
producing degraded resolution within specified regions of specified
frames of a video signal.
Inventors: |
Sugahara; Takayuki (Yokohama,
JP) |
Assignee: |
Victor Company of Japan, Ltd.
(Yokohama, JP)
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Family
ID: |
12784390 |
Appl.
No.: |
09/991,988 |
Filed: |
November 26, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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469499 |
Dec 22, 1999 |
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940941 |
Sep 20, 1997 |
6212329 |
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391861 |
Feb 22, 1995 |
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Foreign Application Priority Data
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Feb 22, 1994 [JP] |
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6-47762 |
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Current U.S.
Class: |
375/240.01;
386/E9.05; G9B/27.019; G9B/20.002; G9B/20.001; 386/261;
386/253 |
Current CPC
Class: |
G11B
20/00007 (20130101); G11B 20/00739 (20130101); G11B
27/3027 (20130101); H04N 9/87 (20130101); G11B
20/00094 (20130101); G11B 20/00086 (20130101); G11B
27/105 (20130101); G11B 20/00188 (20130101); G11B
20/00768 (20130101); G11B 20/00159 (20130101); G06F
21/10 (20130101); H04N 5/85 (20130101); H04N
9/806 (20130101); G11B 2020/10537 (20130101); H04N
9/8042 (20130101); G11B 2220/2545 (20130101); G06F
2221/2149 (20130101); G06F 2211/007 (20130101); G06F
2221/2107 (20130101); G06F 2221/2113 (20130101); G11B
2020/00014 (20130101); G06F 2221/0731 (20130101); G06F
2221/2101 (20130101) |
Current International
Class: |
G06F
21/00 (20060101); G11B 27/10 (20060101); G11B
20/00 (20060101); H04N 9/87 (20060101); H04N
9/804 (20060101); H04N 5/84 (20060101); G06F
1/00 (20060101); H04N 5/85 (20060101); H04N
9/806 (20060101); H04N 007/12 () |
Field of
Search: |
;375/240.01,240.25,240.26 ;386/94 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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33 14783 |
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Oct 1984 |
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DE |
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0 503 519 |
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Sep 1992 |
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EP |
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0 553 545 |
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Aug 1993 |
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EP |
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0 580 367 |
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Jan 1994 |
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EP |
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2 209 417 |
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May 1989 |
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GB |
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5-158531 |
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Oct 1993 |
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JP |
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5-347744 |
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Dec 1993 |
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JP |
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WO 90/13118 |
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Nov 1990 |
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WO |
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Other References
International Standards for Multimedia Encoding, Chapter 6, YASUDA,
Maruzen Co., Japan (cited at pp. 9-10 of original
specification)..
|
Primary Examiner: Lee; Young
Attorney, Agent or Firm: Gopstein; Israel Clark &
Brody
Parent Case Text
This application is a continuation of application Ser. No.
09/469,499 filed Dec. 22, 1999, which is a division of application
Ser. No. 08/940,941 filed Sep. 20, 1997, now U.S. Pat. No.
6,212,329, which is a continuation of application Ser. No.
08/391,861 filed Feb. 22, 1995, abandoned.
Claims
We claim:
1. A data medium for transferring main data to a reproduction
apparatus for reproduction by the reproduction apparatus,
characterized in that: said data medium also transfers medium
protection data which are specific to each of predetermined data
pieces within said main data and are also conveyed by said data
medium; said data medium also transfers protection position
information which specifies a position of said predetermined data
pieces within said main data at which to apply reproduction
protection, said protection position information also being
conveyed by said data medium; the reproduction apparatus generates
apparatus protection data which comprise at least first apparatus
protection data and second apparatus protection data, wherein said
first apparatus protection data are specific to a region or country
in which the reproduction apparatus is to be used, said first
apparatus protection data can not be modified by a user of the
reproduction apparatus; said second apparatus protection data can
be modified by the user to selectively define a plurality of
protection levels including at least two levels which are
respectively specific to adults and to children, and said medium
protection data and apparatus protection data in combination
specify a degree of restriction on said reproduction of the main
data by the reproduction apparatus, wherein the combination of said
medium protection data and said first apparatus protection data
specifies that said main data are reproduced either in their
entirety or not at all, and the combination of said medium
protection data and said second apparatus protection data specifies
that said main data are reproduced in their entirety, partially, or
not at all, wherein said data medium conveys both said medium
protection data and said main data in an identical form.
2. A reproduction protection method for operating on main data
which are conveyed by a data medium, the method comprising the
steps of: detecting medium protection data which are specific to
each of predetermined data pieces within said main data and are
also conveyed by said data medium; detecting protection position
information which specifies a position of said predetermined data
pieces within said main data at which to apply said reproduction
protection, said protection position information also being
conveyed by said data medium; limiting reproduction of said main
data based upon at least a film classification system; generating
apparatus protection data which comprise at least first apparatus
protection data and second apparatus protection data, wherein said
first apparatus protection data are specific to a region or a
country in which said main data are to be reproduced, and can not
be modified by a recipient of said reproduced main data, and
wherein said second apparatus protection data can be modified by
the recipient to selectively define a plurality of protection
levels including at least two levels which are respectively
specific to adults and to children; defining a protection level
based on said medium protection data and said apparatus protection
data in combination; and executing reproduction of said main data
in accordance with said protection level, wherein the combination
of said medium protection data and said first apparatus protection
data determines whether said main data are reproduced in their
entirety or not at all, and the combination of said medium
protection data and said second apparatus protection data
determines whether said main data are reproduced in their entirety,
partially, or not at all, wherein said data medium conveys both
said medium protection data and said main data in an identical
form.
3. A reproduction protection method in accordance with claim 2,
wherein said step of executing reproduction of said main data
comprises: reproducing said main data either in their entirety or
not at all, in accordance with said combination of said medium
protection data and said first apparatus protection data, and
reproducing said main data in their entirety, partially, or not at
all, in accordance with said combination of said medium protection
data and said second apparatus protection data.
Description
DESCRIPTION
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data reproduction protection
method, and a data reproduction apparatus for implementing such a
protection method, whereby reproduction of a signal represented by
digital data such as a recorded digital video signal can be
selectively restricted.
2. Description of the Prior Art
In the following, the term "data medium" is to be understood in a
very general sense, as applying for example to broadcasting systems
which transmit data such as video and/or audio data, in which case
the received data may be the object of reproduction protection, and
as applying also to any type of recording medium such as recording
disks or tapes, etc., in which case playback data derived from the
recording medium may be the object of reproduction protection. The
reproduction protection may serve to selectively restrict viewing,
hearing or copying of the data.
In the prior art, various types of reproduction protection method
have been applied in fields such as CATV (cable television) and
satellite television broadcasting. One method is to execute
scrambling processing of transmitted video and audio data, and to
insert a copyright code into the data, for thereby dividing the
data into portions which can be freely reproduced and portions for
which a fee must be paid in order to reproduce the data. When a
program for which payment of a fee is necessary is received by a
receiving apparatus, the program can be unscrambled and reproduced
only if specified payment conditions are satisfied.
In the case of recorded media, one method of reproduction
protection which is applicable to the DAT (digital audio tape
recorder) recording system is the SCMS (serial copy management
system). With that method, the playback DAT signal from a DAT
playback apparatus has a main ID (identification) number which
includes a copy inhibit code, whereby a single [copy enable-copy
inhibit] sequence is ensured, so that a user can only make a single
copy of a pre-recorded digital audio tape.
However with such prior art methods of reproduction protection
there are only two control possibilities, i.e. reproduction is made
either possible or impossible. It has not been possible hitherto to
provide a gradually varying degree of restriction of reproduction
of a signal conveyed by a data medium. Thus, such a reproduction
protection method can only be used for a single purpose, e.g. for
management of payment fees, or for copyright protection. Moreover
with such a prior art reproduction protection method, since the
data which are to be protected exist only in a transmitting medium
or recording medium prior to being reproduced, it has not been
possible to provide a varying degree of limitation of reproduction
capability in accordance with some condition of the reproduction
apparatus. Thus in some cases, the degree of protection may be
excessively severe, or excessively lax, so that it is difficult to
achieve an effective degree of protection. For example, certain
types of scenes recorded on a video tape may be permitted to be
viewed in a certain country, such as the U.S.A., but may not be
permissible in other countries. It would thus be advantageous to
ensure that when that video tape is played on a reproduction
apparatus which is sold to the public in such other countries,
reproduction protection is automatically applied such that the
aforementioned scenes will not be reproduced, or will not be
clearly reproduced. However in the prior art, such a feature has
not been possible.
SUMMARY OF THE INVENTION
It is an objective of the present invention to overcome the
problems of the prior art set out above, by providing a
reproduction protection method and apparatus whereby information
specifying a degree of restriction of reproduction of an original
signal is conveyed (e.g. by a recording medium or signal
transmission medium) together with data expressing the original
signal, whereby information specifying a degree of restriction of
reproduction of the original signal are generated by a reproduction
apparatus which operates on the conveyed data, and whereby
information specifying a degree of restriction which is actually
applied to reproduction of the original signal is derived based on
a combination of the restriction information conveyed by the data
medium and the restriction information generated by the
reproduction apparatus.
More specifically, the invention provides a reproduction protection
method comprising: attaching medium protection data to main data
which are conveyed by a data medium, said main data representing an
original signal; supplying the main data and medium protection
data, via the data medium, to a reproduction apparatus; generating
apparatus protection data by the reproduction apparatus;
determining a protection level by combining the medium protection
data and the apparatus protection data; and controlling the
reproduction apparatus to utilize the main data to reproduce the
original signal in accordance with the protection level.
It is a further objective of the invention to overcome the above
problems by providing a reproduction apparatus providing
reproduction protection, for operating on main data representing an
original signal and medium protection data expressing a medium
protection level, said main data and medium protection being
conveyed by a data medium, the apparatus comprising: means for
detecting said medium protection data to obtain a medium protection
signal expressing said medium protection level; means for
generating an apparatus protection signal expressing an apparatus
protection level which has been assigned to said reproduction
apparatus; means responsive to said medium protection signal and
apparatus protection signal for determining a final protection
level in accordance with a combination of said medium protection
level and apparatus protection level; means for executing
reproduction of said original signal by utilizing said main data,
including means for selectively restricting said reproduction in
accordance with said final protection level.
With such a method and apparatus for reproduction protection, the
protection level can be determined in accordance with the medium
protection data, and hence can be determined in accordance with the
wishes of the manufacturer of the data medium, or of the copyright
owner of the main data. In addition, the protection level which is
actually applied (i.e. the final protection level) is also
determined in accordance with the apparatus protection data, which
can be specified by the manufacturer or the seller of the
reproduction apparatus. As a result, when the main data are to be
reproduced (for example, during playback of a recording disk or
tape), a graduated degree of limitation of reproduction is
implemented, with that degree of limitation being determined by the
final protection level, i.e. being determined in accordance with a
combination of the requirements of the data medium manufacturer or
the copyright owner of the main data and the requirements of the
manufacturer or seller of the reproduction apparatus. In that way,
considerable flexibility can be ensured in selectively restricting
reproduction of signals which are conveyed for example by recording
disks or tapes or by broadcasting systems.
In particular, the invention enables such reproduction restriction
to be applied to specific frames or sequences of frames of a video
signal, or to specific regions within each of a sequence of
frames.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a general system block diagram of a first embodiment of
the invention, which is a CD player providing reproduction
protection in accordance with the present invention, for use in
describing the basic principles of the invention;
FIG. 2 is a matrix diagram showing an example of how final
protection levels are determined in a reproduction apparatus
according to the present invention;
FIG. 3 shows specific examples of how medium protection levels can
be assigned;
FIG. 4 shows specific examples of how apparatus protection levels
can be assigned;
FIG. 5 is a general system block diagram of a second embodiment,
which is a specific configuration for the apparatus of FIG. 1,
wherein protection control is applied to a data decompression
section;
FIG. 6 shows examples of relationships between final protection
level values and video picture visibility grades, for three
different methods of protection control of a video signal;
FIG. 7 is a general system block diagram of a third embodiment,
which is a specific configuration for the apparatus of FIG. 1,
wherein protection control is applied to a video reproduction
control section;
FIG. 8 is a conceptual diagram for describing how time-axis
protection and spatial-domain protection control can be applied to
a video signal with the present invention;
FIG. 9 is a diagram for describing how video, audio and protection
data can be conveyed in a data stream in accordance with the MPEG1
standards;
FIG. 10 is a block diagram of an example of the internal
configuration of a video reproduction control section in the
embodiment of FIG. 7;
FIG. 11 is a general system block diagram of a fourth embodiment,
which is a specific configuration for the apparatus of FIG. 1,
wherein protection control is applied to a video reproduction
control section and also to an audio reproduction control
section;
FIG. 12 shows examples of relationships between final protection
level values and audio signal audibility grades, for three
different methods of protection control;
FIG. 13 is a block diagram of an example of the internal
configuration of an audio reproduction control section in the
embodiment of FIG. 11;
FIG. 14 is a matrix diagram for illustrating how variable ranges
can be defined for final protection level values, by a fifth
embodiment of the invention;
FIG. 15 is a general system block diagram of the fifth embodiment,
wherein a final protection level can be modified by operation of a
switch provided on the reproduction apparatus; and
FIG. 16 shows relationships between medium protection level values
and settings of a modification switch in the embodiment of FIG. 15,
for each of respective values of the apparatus protection
level.
DESCRIPTION OF PREFERRED EMBODIMENTS
Embodiments of the invention will now be described, in which the
data medium is assumed to be a recording medium, specifically a CD
(compact disk), having video and audio signal data recorded
thereon. In the following, such data representing original signals
which are to be reproduced from the data medium will be referred to
in general as the main data, to distinguish these from protection
data, which are also conveyed by the data medium as described
hereinafter. It will further be assumed that the original video and
audio signals have been encoded by high-efficiency compression
encoding using the MPEG1 algorithm, prior to recording. The MPEG1
algorithm is described for example in "International Standards for
Multimedia Encoding", edited by Yasuda, published by the Maruzen
company in Japan. FIG. 1 is a diagram for describing the general
features of the reproduction protection method and reproduction
protection apparatus.
Protection Information Provided on Recording Medium
The concept of medium protection data will first be described,
referring to FIG. 1, in which data recorded on a CD (compact disk)
1 are read out from the disk to obtain an input signal for a
demultiplexer 10 of a CD player 2, which is shown in block diagram
form and which is configured to provide reproduction protection
control in accordance with the present invention. The CD 1 has
video and audio signals recorded thereon as digital data (referred
to in the following as the main data), using MPEG1 compression
encoding. Protection data, which are predetermined in accordance
with the contents of the main data and will be referred to as the
medium protection data, are also recorded on the CD 1. The medium
protection data consist of information to be used in selectively
restricting reproduction of the main data, as described
hereinafter. The medium protection data can for example be recorded
within the main code and sub-code header regions of the CD 1, or in
the user region of the compressed data. The medium protection data
expresses a protection level, referred to as the medium protection
level, which can for example take values which successively
increase in five steps, from 1 to 5, as shown in FIG. 2 and
described hereinafter. In that case, the medium protection data can
express the medium protection level by 3 bits. If separate medium
protection levels are provided for the recorded video and audio
data, then these can be expressed by two sets of 3 bits. The higher
the number of the medium protection level, the greater is the
degree of protection (i.e. the greater becomes the degree of
restriction of reproduction of the recorded video or audio signal).
The limitation of reproduction can for example by effected, in the
case of video data, by operating on the playback data obtained from
the CD 1 such as to produce an output video signal, from the
apparatus of FIG. 1 which will result in a mosaic pattern being
produced within all or a specific region of a resultant displayed
picture, as described hereinafter.
The medium protection level which is expressed by the medium
protection data is predetermined in accordance with the wishes of
the manufacturer or seller of the data medium (CD 1), or of the
owner of the copyright for the main data. FIG. 3 shows two examples
of medium protection data, each expressing 5 values of medium
protection level. In the first example, limitation of reproduction
is based upon the film classification system (i.e. movie ratings
system) which is used in the U.S.A. In the case of a film which is
rated "free", no restriction on reproduction is imposed by the
medium protection data. If the movie is rated "PG" (i.e. parental
guidance), then a moderate degree of restriction (protection level
1) is applied, and so on with increasing degrees of restriction for
the "R" and "X" ratings. In the second example, limitation of
reproduction is based on the rights of the copyright owner,
providing successively increasing degrees of restriction of
reproduction as the protection level increases from 1 to 5.
The medium protection data is a combination of data for expressing
at least one medium protection level as described above, and
protection position information which specifies the position
(within the encoded main data) at which the protection is to be
applied. It is an essential feature of the present invention that
the medium protection data can assign the medium protection level
in units of frames of the video signal. That is to say, limitation
of reproduction of individual frames can be controlled. In
addition, limitation of reproduction of one or more specific
regions within a specific frame (or sequence of specific frames)
can also be predetermined by the medium protection data. In that
case, for example, a region formed of a number of fixed-size blocks
of pixels can be converted to a blank region, or filled with a
mosaic pattern, in the final display picture that is obtained from
the output video signal from the apparatus of FIG. 1. That is to
say, the protection position information can be used to specify not
only a specific frame, but also to specify one or more specific
regions within a frame.
Alternatively, the protection position information can specify an
identical medium protection level for the entirety of each of a
succession of video signal frames, or specify an identical medium
protection level for one or more specific regions within each of a
succession of frames.
The term "protection position information" is used here, since it
may not be necessary to record explicit data constituting the
protection position information on the CD 1. Instead, that
information can be inherently constituted by the positions at which
respective medium protection data are located within the stream of
compressed encoded main data that have been recorded on the CD 1.
For example, the apparatus may be configured such that if the
encoded data for a video signal frame are immediately preceded by a
portion of medium protection data, then that indicates that the
medium protection data portion is to be applied to that frame. If
the medium protection data portion is to be applied to one or more
regions within that frame, rather than the entire frame, then the
medium protection data portion which immediately precedes the
compressed encoded frame in the recorded data can include at least
two values for each of these regions, for specifying the respective
positions of the regions. In that case, explicit protection
position information must be recorded as data on the CD 1, as part
of the medium protection data.
Protection Information Generated by Reproduction Apparatus
With the method and apparatus of the present invention, a
reproduction apparatus can be configured to produce predetermined
protection data which are specific to that reproduction apparatus.
For example, the CD 1 in FIG. 1 is played by a reproduction
apparatus 2 which is provided with a presettable memory device
which will be assumed to be a ROM (read-only memory) which
generates apparatus protection data expressing a protection level
referred to in the following as an apparatus protection level. The
apparatus protection level is specified beforehand by the
manufacturer or the seller of the reproduction apparatus. In the
same way as for the medium protection data described above, the
apparatus protection level can take a plurality of values,
corresponding to respectively different degrees of limitation of
reproduction of main data which are obtained from a data medium. It
will be assumed that the number of apparatus protection level
values is 4, i.e. from 1 to 4, so that the apparatus protection
data can consist of two bits. The higher the apparatus protection
level number, the greater becomes the degree of protection, i.e.
the greater becomes the degree of reproduction limitation.
The contents of the apparatus protection data ROM cannot be
rewritten by the user. In the embodiment of FIG. 1, each time that
power to the apparatus is switched on, the apparatus protection
data are read out from the ROM, and thereafter reproduction is
executed in accordance with a combination of the apparatus
protection level specified by the apparatus protection data and the
medium protection level which is specified by the medium protection
data.
FIG. 4 shows three examples of how the apparatus protection level
can be assigned. In the first example, the apparatus protection
level is preset in accordance with the country in which the
reproduction apparatus is to be used. If the reproduction apparatus
is to be used in the U.S.A. for example, then it is possible that
the apparatus protection level could be set to a low value such as
1. In the case of a reproduction apparatus which is to be used in
other parts of the world, such as Europe, Japan and Taiwan, which
have varying degrees of restrictions on video software, the
apparatus protection level could be set to higher values, as
illustrated. In that way, video scenes which are not permissible in
one country can be automatically eliminated (partially or
completely), e.g. by insertion of mosaic pattern regions in the
resultant display picture, by using the apparatus protection level
and medium protection level in combination as described
hereinafter.
With the second example in FIG. 4, the apparatus protection level
is predetermined in accordance with the type of person who is
expected to use the reproduction apparatus. If the reproduction
apparatus is to be used only by adults, for example, then the
apparatus protection level can be set at a low value such as 1. If
the reproduction apparatus will be used by children, the apparatus
protection level can be set to a high value such as 4. In that way,
video scenes or audio content which are considered unsuitable for
children can be partially or completely restricted from being
reproduced.
With the third example in FIG. 4, the protection level that is set
by the apparatus protection data is predetermined in accordance
with the applications for which the reproduction apparatus will be
used. For example if the reproduction apparatus is to be sold to
the public, then the apparatus protection level can be set to a
value such as 1 or 2, whereas if the reproduction apparatus is
intended to be used for demonstration purposes in a shop, then the
apparatus protection level can be set to a different value, i.e. 3
or 4, and the apparatus of FIG. 1 controlled such that only certain
scenes which should be of interest to possible customers of the
shop will be displayed. In that way, the apparatus protection level
can be set in accordance with the application objectives of the
reproduction apparatus.
The overall features of reproduction protection will now be
described, referring to FIG. 1. Firstly, data recorded on the CD 1
are read out, as an input signal to the demultiplexer 10. The
recorded data on the CD 1 consist of the compressed encoded main
data (i.e. compressed encoded video and audio data) which are
multiplexed with the medium protection data. The demultiplexer 10
separates the compressed encoded main data from the medium
protection data, and supplies the medium protection data to a
medium protection signal detection section 11 while supplying the
compressed encoded main data to a video decoder section 15. As
described hereinabove, the medium protection data may inherently
specify protection position information, or may include explicit
protection position information. The medium protection signal
detection section 11 serves to detect the protection position
information, and generates a corresponding protection position
signal, which indicates those portions of the main data to which
the medium protection data applies (e.g. specific video signal
frames, and/or block regions within specific frames). The
protection position signal is supplied to a protection control
signal generating section 14. The medium protection signal
detection section 11 is further responsive to the medium protection
data for generating a corresponding medium protection signal, which
expresses the medium protection level and is supplied to a final
protection level determining section 13.
The final protection level determining section 13 basically
consists of a matrix ROM in this embodiment, i.e. a ROM which
stores a pattern of relationships between respective combinations
of medium protection levels and apparatus protection levels and
resultant final protection levels. The operation of the matrix ROM
will be described referring to the matrix diagram of FIG. 2, which
shows an example of how the contents of that ROM are read out in
response to combinations of medium protection level and apparatus
protection level values. There are five possible values (designated
as A to E respectively) for the final protection level,
successively increasing in degree of reproduction limitation in the
sequence A, B, C, D, E. FIG. 2 shows an example of various values
of the final protection level which are determined by respective
combinations of values of the medium protection level and apparatus
protection level, i.e. the values in the range A to E which are
located at respective intersections between rows and columns of the
matrix in FIG. 2. Thus for example if the medium protection level
is 4 and the apparatus protection level is 2, then the final
protection level will be B.
It is necessary to clearly distinguish between the ROM of the
apparatus protection signal generating section 12 and the matrix
ROM of the final protection level determining section 13. The
contents of the ROM of the apparatus protection signal generating
section 12 can be set in accordance with the requirements for a
particular reproduction apparatus, whereas the contents of the
matrix ROM of the final protection level determining section 13
will in general be common to a large number of reproduction
apparatus units.
The final protection level determining section 13 generates an
output signal, referred to as the final protection level signal,
which expresses the final protection level that has been
determined, and supplies that signal to the protection control
signal generating section 14. In response to that signal, and the
protection position signal, the protection control signal
generating section 14 generates a signal referred to as the
protection control signal, which is supplied to control a section
which will be referred to as the video decoder section 15. For
simplicity of description, only video signal reproduction will be
considered at this stage, and the video decoder section 15 should
be understood as a section which converts the compressed encoded
video data (main data) from the demultiplexer 10 to a standard
(analog) video signal. As the stream of compressed encoded main
data flows into the video decoder section 15 from the demultiplexer
10, the protection control signal controls the video decoder
section 15 such as to apply reproduction protection in accordance
with the final protection level values, at the respective positions
within that data flow which are specified by the protection
position information. The video decoder section 15 thereby produces
an output video signal which will result in video pictures in which
reproduction of the main (video) data is limited in accordance with
the final protection level values. As will be understood from the
above, the final protection level values may change from frame to
frame of the video signal, in accordance with changes in the medium
protection level.
A first example of limitation of reproduction in accordance with
the final protection level will be described, which is implemented
by controlling the expansion and decoding of the main data by the
video decoder section 15. The example will be described referring
to the embodiment of FIG. 5, in which the reproduction apparatus is
again a CD playback apparatus, designated by numeral 3. Only the
operation with regard to the video data of the main data from the
CD 1 will be described. In FIG. 5, a specific configuration for the
video decoder section 15 of FIG. 1 is shown, made up of a
variable-length decoding section 15a, a dequantizer section 15b, an
inverse transform section 15c and a video reproduction control
section 15d, with the compressed encoded video data being supplied
from the demultiplexer 10 to the variable-length decoding section
15a and with the final output (analog) video signal being produced
from the video reproduction control section 15d. In this
embodiment, the video data have been recorded on the CD 1 after
being subjected to compression by discrete cosine transform
processing, and reproduction limitation is controlled by
controlling the accuracy of inverse DCT (discrete cosine transform)
processing which is effected by the inverse transform section 15c.
The protection control signal which is produced from a protection
control signal generating section 14a and supplied to control the
inverse transform section 15c is derived based on the medium
protection data and apparatus protection data, in combination, as
described above for section 14 in FIG. 1, i.e. the protection
control signal applies control in accordance with the final
protection level.
The demultiplexed compressed encoded video data read from the CD 1
are subjected to variable-length decoding in the variable-length
decoding section 15a, and then to dequantization in the dequantizer
section 15b. The resultant compressed data are then subjected to
inverse DCT processing in the inverse transform section 15c, with
the transform processing being selectively modified in accordance
with the protection control signal. The resultant decompressed data
are then processed in the video reproduction control section 15d to
obtain the final output video signal. The effect of reproduction
limitation controlled by the protection control signal acting on
the inverse transform section 15c is to selectively produce a
degree of blurring or formation of a mosaic pattern within the
pictures which are displayed using the final output video signal.
Such a degree of blurring will be referred to as the visibility
grade. An example of the relationship between the visibility grade
and the final protection level values A to E (which are determined
by the protection control signal generating section 14a as
described hereinabove, and are expressed by the protection control
signal) is shown in the leftmost column of FIG. 6. If the
protection level is A, i.e. minimum limitation of reproduction of
the video data, then the protection control signal is set to a
state whereby it does not affect the operation of the inverse
transform section 15c. If the protection level is B, then the
protection control signal controls the inverse transform section
15c such as to operate on a block size of 8.times.8 picture
elements (i.e. the same block size which was utilized in the
original DCT processing), using the DC component value for each
block, but using only two of the AC transform coefficients, with
the values of all of the other transform coefficients being
forcibly set to zero. This will result in a substantial lowering of
resolution of a display picture that is produced based on the
output video signal. If the protection level is C, then the
protection control signal controls the inverse transform section
15c such as to operate on a block size of 8.times.8 picture
elements of a video signal frame, using only the DC component for
each block, (i.e. the DC component is the only transform
coefficient used). In this case, since all of the picture elements
within an 8.times.8 picture element block will have identical video
signal values, this will result in a mosaic pattern being formed in
the finally obtained picture. If the protection level is D, then
the protection control signal controls the inverse transform
section 15c such as to operate on a block size of 16.times.16
picture elements, using only the DC component values. This will
again result in a mosaic pattern being formed, in which the blocks
of the pattern are of larger size then for the case of protection
level C, i.e. a mosaic pattern of macroblocks is formed, thereby
further degrading the degree of visibility of the resultant
picture. If the protection level is E, then the video data obtained
from the inverse transform section 15c are replaced by different
video data (produced from a source not shown in the drawing), which
are produced from the video reproduction control section 15d as the
final video signal, and which will produce a predetermined picture
or pictures. Such a predetermined picture might for example display
a warning message concerning copyright protection.
With the MPEG1 algorithm, a block size of 8.times.8 picture
elements is used in the DCT processing. The transformed block is
expressed by a DC component (i.e. DC coefficient) and a plurality
of coefficients (the AC coefficients) which represent signal level
values at respectively different successively increasing
frequencies. Thus if for example the inverse transform section 15c
is controlled such that only the DC coefficient and the two
lowest-frequency AC coefficients are used, in the inverse DCT
operation for each block, then a specific reduction in resolution
of all (or a specific part) of the resultant display picture can be
achieved in a very simple manner.
Similarly if only the DC component for a block is used in the
inverse DCT processing, with all of the AC coefficients set to
zero, then all of the signal level values for the picture elements
of a block will be set to an identical value, in the resultant
video signal obtained from the inverse DCT operation. Hence, a
mosaic pattern can very easily be formed in the resultant picture
that is obtained using the final output video signal. Moreover if,
for each of respective 16.times.16 element macroblocks (i.e. each
consisting of four 8.times.8 picture element blocks), only the DC
coefficient for a specific one of the 8.times.8 element blocks is
used (for example, the DC coefficient for the upper leftmost one of
the 8.times.8 element blocks) in the inverse DCT processing for all
of the four 8.times.8 element blocks constituting the 16.times.16
element macroblock, with all of the AC coefficients set to zero,
then a mosaic pattern will be formed which is substantially coarser
than the mosaic pattern which is formed by using the 8.times.8
element blocks.
It can thus be understood that with the above embodiment of the
invention, applied to video data which have been subjected to
high-efficiency compression encoding using a data transform
operation, stepwise changes in a degree of restriction of
reproduction of the video data can be easily accomplished by
effecting stepwise changes in a degree of resolution of a finally
obtained picture, or in a portion of that picture, and that such
stepwise changes in resolution can be easily controlled in
accordance with the final protection level which has been
established based on the medium protection data and apparatus
protection data. In particular, when such control is applied to the
inverse DCT processing, it is possible to easily effect stepwise
changes in the visibility grade, i.e. in the picture resolution,
through use of unit blocks of picture element values which are
basic to the transform processing. Such a type of control of the
visibility grade, operating within each frame of the video signal,
can be considered as applying protection in a (2-dimensional)
spatial domain.
With a video data encoding method such as the DCT method, the
output digital signal that is produced from the inverse DCT circuit
consists of sequential sets of data, each consisting of successive
picture element values for the respective picture elements of a
unit block (e.g. a block of 8.times.8 picture elements) of a video
signal frame. In order to convert such a digital signal into a
normal digital video signal, it is necessary to first temporarily
store the data produced from the inverse DCT circuit in a video
memory (e.g. a frame memory), then to read out the video data in
the correct sequence (i.e. as successive picture element values in
successive picture scanning line intervals). That operation is the
basic function of the video reproduction control section 15d in
FIG. 5. FIG. 7 shows another embodiment of the invention, in which
control for reproduction protection is applied to the video data
which have been produced from the inverse transform section 15c,
i.e. in which control by the protection control signal in
accordance with the final protection level is applied to a video
reproduction control section which is configured such as to respond
appropriately to the protection control signal, and is designated
as 15d'. Apart from this feature, the configuration and operation
of this embodiment is identical to that of FIG. 5 described above.
The video reproduction control section 15d' includes a frame
memory, into which output data from the inverse transform section
15c are temporarily written, and then read out in the appropriate
sequence as described above, to obtain the final output video
signal.
In this embodiment, the degree of reproduction limitation is
controlled by "thinning out" frames of the video data that are used
to form the final output video signal, with the degree of "thinning
out" being determined by the final protection level. That is
illustrated by the central column in FIG. 6, in which such a type
of control is referred to as time domain protection. In the example
of FIG. 6, when the final protection level is A, then all of the
frames of video data which are successively written into the frame
memory of the video reproduction control section 15d' are used to
form the final output video signal. If the final protection level
is B, then the protection control signal from the protection
control signal generating section 14b controls the video
reproduction control section 15d' such that only one out of every
15 frames of video data supplied from the inverse transform section
15c is used to form the final output video signal. Specifically,
one out of every fifteen frames of video data from the inverse
transform section 15c is held stored in the frame memory of the
video reproduction control section 15d' for fifteen successive
frame periods, and is repetitively read out during that time, to
form the final output video signal. Thus a type sample-and-hold
operation is performed using the frame memory in the video
reproduction control section 15d', whereby the finally obtained
picture will change once in every 0.5 seconds. If the final
protection level is C, then the video reproduction control section
15d' is controlled such that the contents of the frame memory are
updated only once in every 60 frame periods, i.e. the finally
obtained picture will change only once in every 2 seconds. If the
final protection level is D, then only the video data of certain
specific frames (or one specific frame) are written into the frame
memory of the video reproduction control section 15d' and read out
to obtain the final output video signal. In that way, for example,
only a portion of the video data (e.g. a portion which is not
subject to copyright protection) will be displayed. If the
protection level is E, then the video data for a predetermined
picture are written into the frame memory of the video reproduction
control section 15d' and repetitively read out, to display only
that predetermined picture, which can be for example a warning
message concerning copyright protection.
Alternatively, control of the degree of reproduction limitation can
be performed by arranging that the protection control signal from
the protection control signal generating section 14b acts on the
video reproduction control section 15d' such as to vary (in
accordance with the final protection level) the number of
gradations provided by each video data sample, i.e. to vary the
number of amplitude levels that can be expressed by each sample.
That can be performed by setting one or more low-order bits of each
data sample to a fixed value, e.g. 0. For example if the LSB is
always set to 0, then the number of possible gradations is reduced
by half, and a corresponding lowering of resolution of the finally
obtained display picture is achieved. The bits in each digital data
sample which are not fixed in that way will be referred to in the
following as the effective bits of the sample. Such gradation
control based on the numbers of effective data bits is illustrated
by the right-side column in FIG. 6. In that example, if the final
protection level is A, then the protection control signal from the
protection control signal generating section 14b has no effect on
the operation of the video reproduction control section 15d', so
that each video data sample used to form the output video signal
has the standard number of effective bits, i.e. 8 bits. If the
final protection level is B, then the protection control signal
controls the video reproduction control section 15d' such that the
number of effective bits/sample of the output video signal is
reduced to 4 (i.e. by rounding-off the low-order 4 bits to zero).
If the final protection level is C, then the protection control
signal controls the video reproduction control section 15d' such
that the number of effective bits/sample is 2 (i.e. all except the
two high-order bits are set to zero), so that the picture
resolution is further degraded. Similarly, if the final protection
level is D, then the video reproduction control section 15d' is
controlled such that the number of effective bits is reduced to 1.
If the protection level is E, then the video data for a
predetermined picture are written into the frame memory of the
video reproduction control section 15d' and repetitively read out
as the final output video signal, to display only that
predetermined picture.
It would be equally possible, as indicated by the broken-line
connection from the protection control signal generating section
14b to the dequantizer section 15b in FIG. 7, to arrange that the
protection control signal from the protection control signal
generating section 14b acts on the dequantizer section 15b such as
to vary (in accordance with the final protection level) the number
of effective bits of each output datum from the dequantizer section
15b. That will provide a similar effect to that described above for
the case in which control is effected through the video
reproduction control section 15d'.
Another method which may be used to control the degree of
reproduction limitation is to apply the protection control signal
from the protection control signal generating section 14b such as
to control the variable-length decoding section 15a. In that case,
the protection control signal is arranged to act on the
variable-length decoding section 15a such that, as the protection
level is increased from A to E, data having a long code length are
set to zero, i.e. are ignored. This will result in a lowering of
resolution in the final picture that is obtained from the output
video signal.
It should be noted that reproduction limitation control can be
executed by a combination of control acting along the time axis and
control acting in a spatial domain (i.e. within individual frames).
That point is illustrated conceptually in FIG. 8, in which
successive vertical lines 20 represent sequential frames of the
video signal that is recorded on the CD 1. (For simplicity of
description, it will be assumed that the final protection level is
identical to the medium protection level). Together with each video
signal frame data portion on the CD 1, a medium protection data
portion is recorded, which may include position information
specifying a region within the frame within which display
resolution is to be lowered, to a degree that is in accordance with
the final protection level. In this example there are two possible
basic display conditions for each frame, i.e. non-display or
display (with one or more degraded resolution regions possibly
being formed). To achieve this, the medium protection data assigned
to each frame includes a 1-bit flag, whose 1 or 0 logic state
designates either display or non-display for the frame. If that
flag bit indicates that none of the frame is to be displayed, the
condition is indicated by a "x" symbol in FIG. 8, while if the flag
bit indicates that the frame is to be completely or partially
displayed, that condition is indicated by a "o" symbol in FIG. 8.
In the example of FIG. 8, a "o" condition is specified for each of
the ten consecutive frames designated as F.sub.A, indicating that
each frame is to be displayed. In addition, the medium protection
data of each of these frames includes position information for a
degraded resolution region. The resultant display picture is
designated by numeral 21, containing a degraded resolution region
22, which is rectangular and is shown as a hatched-line region. The
degraded resolution region 22 is formed by a plurality of
16.times.16 element macroblocks, and for each of the frames
F.sub.A, the corresponding position information in the medium
protection data specifies two addresses of macroblocks (designated
as 22a and 22b, located at the upper left-side and lower right-side
corners of the mosaic region 22) within the frame, to thereby
specify the position and size of a rectangular region which is the
degraded resolution region 22.
Similarly, a set of four successive frames F.sub.B is each to be
displayed, but with a degraded resolution region formed in the
final display picture, as indicated by numeral 24. In this case the
degraded resolution region is formed of two adjoining rectangular
regions, so that it is necessary for the position information in
the medium protection data to specify the positions of two pairs of
macroblocks within the frame, i.e. the pair of addresses of
macroblocks 24a, 24b and the pair of addresses of macroblocks 24c,
24d in FIG. 8.
It can thus be understood that in this case, reproduction
protection is applied by a combination of control with respect to
the time axis, and control with respect to (2-dimensional) space
within each frame. It can be further understood that the invention
enables extremely precise control of reproduction limitation, which
is determined in accordance with the final protection level.
With data transmission in accordance with the MPEG1 system (i.e.
based on the ISO-11172-3 standards), data are transmitted as
successive packs of data, which are time-division multiplexed, as
illustrated by the data flow 40 shown in FIG. 9. Each pack is made
up of a leading portion such as the portion 41, which contains
information including a pack start code and a stream identifier
which distinguishes the data conveyed by that pack from that of
other packs (e.g. to distinguish between video, audio or other
data), and a main data portion such as portion 42. In this example
each main portion consists of either compressed encoded video data
such as portion 42, encoded audio data such as portion 43, or
protection data such as portion 44. In this example it will assumed
that protection of the form shown in FIG. 8 is applied to the video
data, so an individual protection data portion may be assigned to
each of a plurality of video signal frames, i.e. video data frames
can be conveyed by respective packs, each preceded by a protection
data pack. In that case, each protection data pack in the example
of FIG. 9 consists of a 3-bit portion which specifies the medium
protection level, a 1-bit frame flag specifying whether or not the
frame is to be displayed (as described above for FIG. 8), a portion
which specifies the number of macroblock start/end address pairs
(to be utilized when at least one degraded resolution region is to
be formed within the frame, e.g. as for each of the frames F.sub.A
and F.sub.B in FIG. 8), followed by the pairs of macroblock
start/end addresses (e.g. the pair of addresses of macroblocks 24a,
24b, then the pair of addresses of macroblocks 24c, 24d, for each
of the frames F.sub.B in the example of FIG. 8).
FIG. 10 shows a specific internal configuration for the video
reproduction control section 15d' of the embodiment of FIG. 7. In
FIG. 10, the output data from the inverse transform section 15c are
supplied via a line 50 to a gradation control section 51, which is
controlled by one of two protection control signals that are
generated from the protection control signal generating section
14b, and resultant output data from the gradation control section
51 are transferred through a switch 52, which is controlled by the
other one of the protection control signals. Data transferred
through the switch 52 are written into a frame memory 53, and are
subsequently read out from the frame memory 53 in the appropriate
sequence to constitute successive frames of the original video
signal. The digital video signal thereby produced from the frame
memory 53 is supplied to a digital/analog converter 54, to obtain
an analog video signal as the final output signal. So long as the
switch 52 is held closed, the contents of the frame memory 53 will
be completely updated once in each frame period of the video
signal, so that data of a new frame will be sequentially read out
from the frame memory 53. However if the switch 52 is held closed
during an integral number of frame intervals, then the most
recently stored contents of the frame memory 53 will be
repetitively read out during each of these frame intervals, i.e.
the last frame will be continuously outputted. It will thus be
apparent that this circuit can implement the time-axis protection
operation described above on successive frames, if the switch 52 is
controlled in accordance with the status of the frame bit that is
contained in the medium protection data.
The gradation control section 51 operates on each digital video
signal sample (in general, each 8-bit datum) that is supplied from
the inverse transform section 15c, to set the low-order bits of
each sample in accordance with the final protection level. For
example referring to the right-side column in FIG. 6, if the final
protection level is B, then the gradation control section 51 sets
all of the four low-order bits of each sample to a predetermined
value, e.g. 0. If the protection level is D, then all of the seven
low-order bits of each sample are set to 0.
If reproduction restriction is to be applied within a video signal
frame, then the protection control signal generating section 14b
responds to the protection position signal such as to apply the
above-mentioned protection control signal to the gradation control
section 51 during one or more specific time intervals within the
corresponding frame interval, with each of these specific time
intervals being determined based on one of the macroblock start/end
address pairs which are shown in FIG. 9, described above. In that
way, reproduction limitation can be applied within specific regions
of a frame, as illustrated in FIG. 8, i.e. the spatial-domain
protection operation described above can be applied.
It will be understood that in practical terms, each "start address"
will define a time-axis position, within a frame period, of the
data sample corresponding to an uppermost left-side pixel of a
rectangular region within the frame, while the "end address"
similarly defines the position of a data sample corresponding to a
lowermost right-side pixel of that region. Such time relationships
can be readily established by well-known techniques for operating
on a digital video signal, so that detailed description is
omitted.
In the above embodiments, only reproduction protection of video
data has been described. FIG. 11 shows another embodiment of the
invention, in which reproduction protection of both audio and video
data is applied. Only the points of difference between this
embodiment and previous embodiments will be described. A CD
reproduction apparatus 5 of this embodiment differs from that of
FIG. 7 by including circuits for decoding and dequantizing an
encoded digital audio signal that has been recorded on the CD 1, by
an audio decoding section made up of a variable-length decoding
section 16a, a dequantizer section 16b, a sub-band combining
section 16c and an audio reproduction control section 16d. The
compressed encoded audio data are separated from the video and
protection data contained in the input data stream, by the
demultiplexer 10, and are supplied as input data to the
variable-length decoding section 16a, with an output audio signal
being produced from the audio reproduction control section 16d.
This embodiment further differs from that of FIG. 7 in that the
protection control signal generating section 14c of this embodiment
produces not only a first protection control signal which acts on
either the video reproduction control section 15d' or dequantizer
section 15b to apply video signal reproduction protection by
varying the number of bits per datum, as described hereinabove for
the protection control signal of the embodiment of FIG. 7, but also
a second protection control signal which acts on the audio
reproduction control section 16d or dequantizer section 16b to
apply audio signal reproduction protection, as described in the
following. For simplicity of description, it will be assumed that
the second protection control signal is produced in accordance with
the final protection level that is derived for reproduction
protection of the the video data, as described hereinabove. However
in general, separate medium protection levels and separate
apparatus protection levels would be specified for the video and
audio data, i.e. to obtain separate final protection levels for
video and audio data.
FIG. 12 is a table illustrating three possible methods of applying
audio signal reproduction protection with the embodiment of FIG.
11. With each of the three examples shown in FIG. 12, five
different audibility grades can be selected for the output audio
signal produced from the audio reproduction control section 16d, in
accordance with the final protection level, to effect audio signal
reproduction protection. Firstly, the method illustrated by the
leftmost column in FIG. 12 will be described. In this case, audio
signal reproduction protection is applied by selectively
restricting the bandwidth of the output audio signal produced from
the audio reproduction control section 16d in accordance with the
final protection level. If MPEG1 audio signal compression is used,
then assuming a sampling frequency of 48 KHz, a bandwidth of 24 KHz
is available for the output audio signal. In this example, if the
final protection level is A, then no bandwidth restriction is
applied, i.e. the audio bandwidth is 24 KHz. If the final
protection level is B, then the audio signal bandwidth is
restricted to 18 KHz, if the protection level is C the bandwidth is
restricted to 12 KHz, if the protection level is D the bandwidth is
restricted to 6 KHz, and if the protection level is E then no audio
output signal is produced.
Since MPEG1 audio compression utilizes sub-band encoding with 32
bands, such bandwidth restrictions can be effected by causing the
second protection control signal to act on the dequantizer section
16b such as to set the inverse quantization values corresponding to
certain high-frequency bands to zero. Thus, audio reproduction
protection by bandwidth control can be easily implemented.
A second method of audio signal reproduction protection will be
described referring to the central column in FIG. 12. In this case,
time-axis protection is applied, by "thinning-out" of audio signal
sample values that are supplied from the sub-band combining section
16c and used in the audio reproduction control section 16d to
obtain the output audio signal. In this example, if the final
protection level is A, then all of the audio sample values are used
in deriving the output audio signal. If the final protection level
is B, then one in every two samples is held for two consecutive
sample periods, by a sample-and-hold circuit, i.e. only half of the
total samples are used in deriving the output audio signal. If the
protection level is C, then only one in every three samples is used
in deriving the output audio signal, i.e. one in every three
successive samples is held for three consecutive sample periods. If
the protection level is D, then only samples which occur during a
specified interval are used in producing the output audio signal.
For example, this operation could be performed when only a
specified part of the recorded audio signal is to be allowed (by
the copyright owner) to be reproduced. If the final protection
level is E, then no audio output signal is produced.
A third method of audio signal reproduction protection will be
described referring to the rightmost column in FIG. 12. In this
case, protection control is executed by effecting control of the
number of gradation levels provided by the audio data samples, in a
similar manner to that described hereinabove for the video data.
Generally, a digital audio signal has 16 bits/sample. When the
final protection level is A, then all of these 16 bits are
utilized, i.e. there is no limitation of audibility. If the final
protection level is B, then the number of effective bits/sample is
reduced to 12 (i.e. the low-order 4 bits of each 16-bit sample are
fixed at 0), causing a lowering of quality of the reproduced audio
signal. If the protection level is C, the number of effective bits
is further reduced to 8, if the final protection level is D then
the number of effective bits/sample is reduced to 4, and if the
final protection level is E, then no audio output signal is
produced.
It can thus be understood that the invention enables precise
limitation of reproduction of a recorded audio signal together with
limitation of reproduction of the recorded video signal, in
accordance with a combination of medium protection data and
apparatus protection data.
FIG. 13 shows an example of the internal configuration of the audio
reproduction control section 16d of this embodiment. For the
purpose of description, it is assumed that each of the
above-mentioned three methods of protection control of the audio
reproduction control section 16d is utilized, although in practice
only one of these could be utilized. The circuit consists of a
digital low-pass filter 61 which receives the output data samples
from the sub-band combining section 16c via an input line 60, a
sample-and-hold circuit 62 which can be controlled to hold and
output each data sample for a specific interval, a gradation
control section 63 which effects the aforementioned control of
low-order bits of each audio data sample, to thereby control the
gradation levels which can be expressed by each sample, a memory 64
for temporarily holding successive data samples, and a
digital-to-analog converter 65 for converting the digital audio
data to an analog audio signal. The gradation control section 63 is
controlled by a protection control signal to provide varying
degrees of gradation in accordance with the final protection level
that has been determined for the audio data, by setting varying
numbers of low-order bits of each 16-bit audio data sample to a
fixed value as described above.
As shown, the protection control signal can also be applied to
control the sample-and-hold circuit 62, to effect the
above-described method of reproduction protection control utilizing
sample-and-hold processing of the audio data samples. Similarly,
the protection control signal can be applied to control the LPF 61,
to achieve reproduction protection control by varying the bandwidth
of the audio signal. It will be clear that a simpler circuit
configuration can be utilized that that shown in FIG. 13, if only
one of the above three methods of protection control is
applied.
In each of the embodiments described above, there is a fixed
relationship pattern between combinations of the protection levels
which can be expressed by the medium protection data and the
protection levels which can be expressed by the apparatus
protection data, and the respective final protection levels which
are thereby obtained, i.e. the relationship pattern which is stored
in the matrix ROM of the final protection level determining section
13, an example of which is shown in FIG. 2. However in some cases
there may be a requirement for enabling such a relationship pattern
to be selected from a number of different relationship patterns,
which have varying degrees of protection severity. Specifically, it
may be advantageous to provide the reproduction apparatus with a
switch which can be operated by the person who is in charge of the
reproduction apparatus, such that the switch can be used to select
from a plurality of different relationship patterns, so that the
degree of reproduction protection can be flexibly determined by
that person. In that way, the person in charge of the reproduction
apparatus can ensure that the reproduction protection will be
appropriate for the viewing audience. For example, an adult can set
the switch such as to ensure that unsuitable scenes cannot be
viewed by any children who may use the reproduction apparatus. In
that case, assuming for example that the relationship pattern which
is the least severe is that shown in FIG. 2, the entire range of
possible relationship patterns is illustrated in the table of FIG.
14. Here, for each combination of protection levels obtained from
the medium protection data and apparatus protection data, there is
a corresponding range of one or more possible values of final
protection level, with that range extending from a least severe
value to the most severe value (i.e. protection level E). One
method of implementing such a capability would be to provide a
plurality of matrix ROMs (or to define a plurality of separate
matrix regions in a ROM), for storing the respectively different
relationship patterns. However an embodiment of the invention will
now be described whereby such a capability can be easily
implemented by a simple modification of any of the embodiments of
the invention that have been previously described.
The embodiment, which is a modification of the embodiment of FIG.
5, is shown in FIG. 15. The embodiment differs from that of FIG. 5
in being provided with a severity modification circuit 30 and a
severity modification setting switch 31. The severity modification
circuit 30 is connected between the final protection level
determining section 13 and the protection control signal generating
section 14a, and functions to selectively modify each protection
level value which is read out from the matrix ROM of the final
protection level determining section 13 (as described hereinabove
for the embodiment of FIG. 5), and to supply a resultant modified
final protection level to the protection control signal generating
section 14a. The severity modification setting switch 31 can be
adjusted by the person who is in charge of the CD player, to select
one of five possible switch conditions which will be designated as
P.sub.A to P.sub.E, respectively. The severity modification setting
switch 31 is coupled to control the severity modification circuit
30 such that the severity modification circuit 30 executes
protection level modification in accordance with the specific
position at which the switch is set, as described in the
following.
The relationships between the five possible values of the medium
protection level (determined by the medium protection signal
detection section 11 as described hereinabove) and the five
positions P.sub.A to P.sub.E of the severity modification setting
switch 31, are shown for each of the four possible values of the
apparatus protection level (determined by the apparatus protection
signal generating section 12), in diagrams (A) to (D) in FIG. 16.
Referring first to diagram (A), if the switch position is P.sub.A,
then the relationship between the medium protection level values,
the apparatus protection level values and the final protection
level values is left unchanged from those of the corresponding
column in FIG. 2, i.e. this setting of the severity modification
setting switch 31 provides the least severe degree of reproduction
protection. If the switch position is set to P.sub.B, then the
least severe value which can be taken by the modified final
protection level becomes level B. That is to say, if a protection
level A is established by the final protection level determining
section 13, that is changed by the severity modification circuit 30
to a modified final protection level B. If the switch position is
P.sub.c, then the least severe value of the modified final
protection level is changed to C. If the switch position is
P.sub.D, then the least severe value of the modified final
protection level is changed to D, and if the switch position is
P.sub.E, then the modified final protection level is fixed as
E.
The same is true for each of the apparatus protection level values
2, 3 and 4, as illustrated in diagrams (B), (C) and (D) in FIG. 16,
which correspond to the second, third and fourth columns in FIG. 2
respectively.
It will be apparent that the severity modification circuit 30 can
be easily configured using a logic circuit, which implements a
simple algorithm in accordance with the setting of the severity
modification setting switch 31, i.e. the algorithm would begin:
[If the severity modification switch 31 is set at P.sub.A, transfer
the protection level value established by the final protection
level determining section 13 directly to the protection control
signal generating section 14a, as the final protection level.
If the severity modification switch 31 is set at P.sub.B, and if
the protection level value established by the final protection
level determining section 13 is level A, change that to level B and
transfer to the protection control signal generating section 14a as
the (modified) final protection level. Otherwise, transfer the
protection level value produced from the final protection level
determining section 13 unchanged, as the final protection
level.
If the severity modification switch 31 is set at P.sub.c, and if
the protection level established by the final protection level
determining section 13 is level A or level B, change to level C,
and transfer to the protection control signal generating section
14a as the final protection level. Otherwise, transfer the
protection level established by the final protection level
determining section 13 unchanged, as the final protection level . .
. ], and so on.
Thus with this embodiment, if the severity modification setting
switch 31 is set to its least severe position (P.sub.A), then the
relationship pattern between combinations of the medium protection
level and reproduction apparatus protection level values will be as
shown in FIG. 2. If the severity modification setting switch 31 is
set to the most severe position (P.sub.E), then the relationship
pattern will be such that the final protection level will always be
the highest level, i.e. level E. As the severity modification
setting switch 31 is successively changed from positions P.sub.A to
P.sub.E, the least severe degree of reproduction restriction
(within the range of possible degrees of restriction which can be
set by the final protection level) is increased to a more severe
degree, by successive steps.
For example if the apparatus protection level is 2 and the medium
protection level is 4, then the final protection level will be B.
However by altering the setting of the severity modification
setting switch 31, the user can change the final protection level
to a higher value, in the range B to E. Hence with this embodiment,
although protection level values can be specified by the
manufacturer or copyright owner of the recording medium, and by the
manufacturer or seller of the reproduction apparatus, the final
degree of protection can be determined by the person who is in
charge of the reproduction apparatus. Such a feature is highly
useful.
As can be understood from the above description of embodiments, the
invention enables a final protection level to be established, for
controlling reproduction of recorded or transmitted video or audio
signals, with that final protection level being determined based on
a combination of protection levels which are respectively
separately established by the manufacturer or copyright owner of
recorded signals (or broadcaster of transmitted signals, or
copyright owner of transmitted signal) and by the manufacturer or
seller of the reproduction apparatus. The final protection level
can be applied such as to achieve extremely precise protection of
reproduction, whereby for example specific frames of a video
signal, and/or specific regions within a frame, can be protected by
restricting reproduction, with the degree of restriction being
variable in a stepwise manner. The invention can at the same time
provide corresponding protection of an audio signal which is being
reproduced in conjunction with a video signal.
Although the invention has been described in the above with
reference to a CD player apparatus, it will be understood that the
invention is not limited in any way to such an apparatus, and is in
general applicable to reproduction protection in any type of
apparatus which reproduces a recorded or transmitted video and/or
audio signal.
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